int Led = 13 ; // define LED Interface
int Shock = 3 // define the percussion Sensor Interface
int val ; // define numeric variables val
 
void setup ()
{
  pinMode (Led, OUTPUT) ; // define LED as output interface
  pinMode (Shock, INPUT) ; // define knock sensor output interface
}
void loop ()
{
  val = digitalRead (Shock) ; // read digital interface is assigned a value of 3 val
  if (val == HIGH) // When the percussion when the sensor detects a signal, LED flashes
  {
    digitalWrite (Led, LOW);
  }
  else
  {
    digitalWrite (Led, HIGH);
  }
}